Cool Stars 14 - Submitted Abstract # 45 This version created on 05 October 2006 Chromospheric Activity in the Solar-Type Stars in M67 Mark Giampapa, National Solar Observatory Jeffrey Hall, Lowell Observatory Richard Radick, Air Force Research Laboratory Sallie Baliunas, Harvard-Smithsonian Center for Astrophysics We present the final results of a long-term spectroscopic study of the Ca II H & K core strengths in a sample of 60 solar-type stars that are members of the solar-age and solar-metallicity open cluster M67. We adopt the HK index, defined as the summed H+K core strengths in 0.1 nm bandpasses centered on the H and K lines, respectively, as a measure of the chromospheric activity that is present. We find that the stellar distribution in our HK index is broader than that for the solar cycle as measured with an identically defined index. Approximately 17% of the M67 sun-like stars exhibit average HK indices that are less than solar minimum. About 7%--12% are characterized by relatively high activity in excess of solar maximum values while 72%--80% of the solar analogs exhibit Ca II H+K strengths within the range of the modern solar cycle. The ranges given reflect uncertainties in the most representative value of the maximum in the HK index to adopt for the solar cycle variations observed during the period A.D. 1976--2004. Thus, 20%--30% of our homogeneous sample of sun-like stars have mean chromospheric H+K strengths that are outside the range of the contemporary solar cycle. Any cycle-like variability that is present in the M67 solar-type stars appears to be characterized by periods greater than about 6 years. ----------------------------------